1. Field of the Invention
The present invention relates to an apparatus for driving a member in a predetermined direction, and specifically relates to an apparatus for driving an optical member such as a lens element and the like along an optical axis.
2. Description of the Related Art
In conventional lens devices, a rotation motor is used as a lens drive actuator. For example, as shown in FIG. 1, a widely used method provides a cam pin 2a that protrudes from a lens frame 2 which holds a lens 1, and is inserted in a channel 4a provided on a cam ring 4 and is inserted in a rectilinear channel (not illustrated) provided on the stationary barrel 3, such that the rotation of the rotation motor 5 is transmitted to the cam ring 4 via, a gear train 6 or the like, and rectilinearly drives the lens 1 by means of the rotation of the cam ring 4 relative to the stationary barrel 3.
A lens device has been proposed which uses a piezoelectric actuator 8 as a lens driving actuator, as shown in FIGS. 2A and 2B. The piezoelectric actuator 8 comprises a stationary member 8a and a drive rod 8b respectively connected to each end in the expansion/contraction direction of a piezoelectric element 8c which expands/contracts when a voltage of a predetermined waveform is applied thereto, and a slider 8x having a friction member 8t friction bonded to the drive rod 8b via the force exerted by a flat spring 8s, such that the slider 8x is driven along the drive rod 8b which reciprocates in conjunction with the expansion/contraction of the piezoelectric element 8c induced by the application of, for example, a sawtooth-like pulse. The lens frame 2 is connected to the slider 8x.
Lens devices using such lens driving actuators are complex in construction. Furthermore, it is structurally impossible to individually drive a plurality of lenses, and even if such were possible, the construction would be of excessively greater complexity, and the cost would increase.